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2,113,945
Patented Apr. 12, 1938
UNITED STATES PATENT OFFICE
Walter WI Pleohner, Piney' River, Va, and
Arthur W. Hixson, Leonia, N. 1., assignors to
National Lead Company, New York. N. Y... a
corporation of New Jersey
No Drawing.
‘
‘
Application November 23, 1934,
Serial No. 754,454
13 Claims.
,
(on. 23-202)
'
a
.
ly ?nely‘ divided, condition, and, therefore, has
been extremely dl?icult to ?lter and impossible
to wash free from impurities contained in the
Our present invention generally relates to ti
tanium oxide pigments having improved proper
ties,_ and more speci?cally to a novel method of
mother liquor. This extreme ?neness of particle - -
, producing a pigment of this type.
It is believed that the hiding power of a pig
size and di?lculty in washing has resulted in
ment is some function of the refractive index
among other properties; the greater the differ
‘calcined products of very poor color and very
low hiding power, entirely unsuitable for use as
ence between, the refractive index of the pigment .
pigments.
a pigment.
‘
‘
We have discovered that under suitable condi
tions, to be disclosed below, titanium dioxide 10
and that of the vehicle in which it may be sus
10 pended the greater will be the hiding power of
the pigment. In this way is partially explained
the relatively high hiding power of the titanium
adapted to pigment uses can be precipitated from
atitanium chloride solution. Furthermore, pi-g
ment’ so obtained shows a remarkably improved
tinting strength and hiding power over titaniumv
Thus the refractive indices of a few
of the common white pigments are:
15 Titanium dioxide (anatase) _____________ __l 2.55' .oxide pigments hitherto offered in the trade. 15
Thus, if tinting strength is'determined by the
Zinc sulphide
2.37 tentative method oi test of the American Society
Lead basic carbonate_______’_ __________ _-__ 1.99. of'Testing Materials, A. S. T. M. Designation: .
Zinc oxide
'
1.90
D332-31T, A. 8. T. M. Tentative Standards 1933,‘
Blane ?xe
Linseed oil
1.64v
-
1.49
525, the highest value shown ‘by old commercial
products is about 1100-1200, whereas our pig
20~
ment gives values of MOO-1500. The hiding pow- ,
Titanium dioxide which has hitherto been com
mercially prepared has always been precipitated ' er of our form of titanium dioxide is correspond
by the hydrolysis of sulphuric acid solutions of» ingly greater. We now ascribe this to the fact
titanium, and, as has been shown by Weiser and that our pigment is in the rutile modi?cation 25
' Milligan: J. Phys. Chem. 38, 513 (1934), such an since it is precipitated from a‘ chloride solution,
and has. therefore, a higher refractive index
than the ordinary titanium dioxide pigment.
oxide always exists as the anatase modi?cation
which has the refractive index indicated in. the
above tabulation.
30
'
_ It has been long known that therefractive in
dex of the rutile modi?cation of titanium dioxide
is 2.71, and, therefore, if titanium dioxide could
be so precipitated as to form rutile’ on calcine
tion, and, furthermore, if the precipitation con
It may be stated, therefore, that it is one of
the primary objects of the present invention to
provide a titaniuinoxide compound which. pos
sesses tinting strength and hiding power greatly
improved over similar types of pigments ‘hitherto
used, and which compound is readily derived
35
ditions, or “hydrolysis conditions” as it is fre
irom. a titanium chloride solution.
We have discovered that titanium dioxide may
quently called in the art, 'were such as to form
particles which on calcination were suitable for be precipitated from a chloride solution in a formv
pigment purposes, a new white pigment far su . highly suitable'for use as a pigment if the pre
perior in hiding power to’the pigment grade cipitation, or hydrolysis, is carried on under such
titanium oxides now commercially available conditions as to give relatively rapid precipita 40
would have been obtained.
"
It, also, was shown by Weiser and Milligan in
the publication cited above that'when titanium
dioxide is precipitated from a chloride solution
45 the rutile modi?cation is always obtained. Ti
tanium dioxide has not been prepared under
such conditions in the past because until the
time of our discovery it was not known how to
precipitate the oxide from a chloride solution
50 and obtain the other properties, (purity, white
ness, proper particle size, ?lterability, etc), nec
essary for the production of a material suitable
for pigment purposes. Titanium diomde which
has been precipitated from chloride solutions by
others has usually been in a pept, or extreme
tlon in the presence of coagulants which prevent
the well-known peptizing action of the chloride
ion. Such suitable conditions involve the addi
tion of relatively concentrated aqueous solutions
of titanium tetrachloride to'a boiling solution of 45
water containing a very small amount of coagu-‘
lant. We have found that negative divalent ions,
as for .exampleoxalate, tartrate or sulphate, be
have as coagulants and cause the hydrous tita 50
nium omdes to be precipitated in a readily ?lter
able and easily
ed state, and when so pre
cipitated the titanium dioxide obtained after
calcination has rerkably high hiding power
and tint
streth m is comparable in all
55,
2,113,945
2
other respects to the titanium pigments previous
ly available.
>
‘
Hence, it is pointed out that another impor
tant object of the invention is to provide tita
5 nium dioxide in the rutile modi?cation, the com
pound being in a non-peptized state and hem!
characterized by its readily ?lterable condition.
Another advantage of our process is that the
titanium oxide prepared by our method is ‘of
10 unique purity. We have not been able to detect
any impurities ‘in our product by any chemical
speci?c description is but illustrative of a typical
embodiment of our invention, and that various
changes may be made in the various ingredients,
steps, temperatures, quantities of the process, and
the uses of the resulting product, without depart»
ing from the spirit of the invention as set forth
in the following claims.
What we claim is:
1. Process for the preparation of ‘pure titanium
dioxide having rutile crystalline structure which 10'
comprises hydrolytically precipitating non-pep
means known to us. On the other hand titanium tized, easily ?lterable, hydrous titanium oxide
“ oxides precipitated .from sulphuric acid solutions. from an aqueous titanium tetrachloride solution ,
containing a small amount of a negative, divalent
analyze about as follows:
coagulating ion, separating the said hydrous 15
15
.
Per cent
titanium oxide and calcining it to rutile crystal
Titanic oxide ____________________ __ 98.3 -99.2 Sulphuric anhydride_____________ .._
Ferric oxide; ___________________ __
Phosphoric ,anhydride_'_ __________ __
20 Water soluble _______________ _'____-
0.010.010.190.23-
0.81
0.02
0.31
0.62
line structure.
comprises adding an aqueous solution of titanium ,20
tetrachloride to hot water containing a small
amount of a negative, divalent coagulating ion,
heating the mixed solutions to hydrolytically
precipitate non-peptized hydrous titanium oxide
in readily fllterable form, separating the so ob
25 to. . It is to be further understood that the fol
25'
tained hydrous titanium oxide and calcining it to
lowing detailed disclosure of the mode of practis
ing our invention is addressed to those skilled in
the art of preparing titanium oxide pigments;
rutile crystalline structure.
,
_
3..Process for the-preparation of pure titanium
dioxide having rutile crystalline structure which
such skilled persons are fully aware of the ap
comprises hydrolytically precipitating non-pep
tized, easily ?lterable hydrous titanium oxide
paratus and manipulations usually utilized in the
art ocl -
‘
dioxide having rutile crystalline structure which
In order that our method of preparation of pure
titanium dioxide in the rutile modi?cation may be
more readily understood we give an example in. de
tail, although we do not wish to be limited there
30
.
2. Process for the preparation of pure titanium
titanium compounds.
from an- aqueous solution of titanium tetra
Titanium tetrachloride is .obtained by the chloride containing a small amount of a. coagu- .
chlorination under reducing conditions of titanif
lant selected from the‘group consisting of the
erous materials. The operation may be carried acids and alkali metal salts of the sulfate, tar 35
35 out so as to yield titanium chloride containing but
trate and oxalate radicals, separating the said
relatively small amounts of impurities. The ti
hydrous titanium oxide and calcining it to rutile
tanium tetrachloride is then dissolved in two crystalline structure.
volumes of cold water yielding a clear aqueous
4. ‘Process for the preparation of pure titanium
40
chloride solution of titanium containing about 15
40 per cent titanium oxide. All the iron present is dioxide having rutile crystalline structure which
comprises adding an aqueous solution of titanium
reduced to the ferrous condition in order to pre
tetrachloride to hot water containing a . small
vent the hydrolysis which ferric salts readily amount of a coagulant selected from the group
undergo. This reduction'may be accomplished consisting of the acids and alkali metal salts
‘many of the known methods, such as by the in
45
45 troduction of metallic zinc; In order to insure the of the sulfate, tartrate and oxalate radicals, heat
ing the mixed solutions to hydrolytically precipi
absence of ferric iron throughout the precipita
tate. non-peptized hydrous titanium oxide in
tion. we prefer to
the solution to a'content readily ?lterable form, separating the so obtained
of two to three grams per ‘liter of titanium oxide hydrous ‘titanium oxide and calcining it at a tem
the titanous state.
' ~
.
perature between 700° C. and 1000° C. to rutile
50 in Having
1000 pounds 8 chloride solution con
crystalline structure.
'
taining 15 per cent titanium. oxide, this is added
5. Process for the preparation of pure titanium
to 10,000 pounds of boiling water containing 10 dioxide having rutile crystalline structure which -‘
pounds of oxalic acid during about one hour. comprises adding an aqueous solution of titanium
When the addition has been completed about 95 tetrachloride to hot water containing a small 55
55 per cent of the titanium will have been precipi
amount of a coagulant selected'from the group
tated as hydrous titanium dioxide; the latter is consisting‘ of the acids and alkali metal salts
in a coagulated form such that it settles well and I of the sulfate, tartrate and oxalateradicals, heat
i may be readily filtered and washed. ‘ After ?ltra
ing the mixed solutions to hydrolytically pre
, tion and washing the precipitate is converted to cipitate non-peptized hydrous titanium oxide in
00 the anhydrous rutile form by calcining at a tem
readily ?lterable form, separating the so ob- ..
perature of from 700° to 1000° C.
tained hydrous titanium oxide and calcining it
While in the above example oxalic acid has been at a temperature between ‘700° C. and 1000° C.
used as the coagulant any substance dissociating j to form a product possessingl'rutile crystalline
so as to produce a divalent negative ion in aqueous
05 solution, sulphuric acid for example, may be used.
structure, a tinting strength between 1400 and
1500' as determined by A. S. T. M. method,
Tartarlc acid, in addition to the oxalic’ and sul
D332-31T, covering power, whiteness, particle
furic, dissociates so as to produce a divalent nega
tive ion in aqueous solution and at the same time
size, and brightness rendering" said product
adaptable for pigment uses.
alkali solution, e. g_., sodium sulfate Na?sod,
sodium oxalate N??ciod, sodium tartrate
NaaCaHrOa etc., may be used.
.15
'
_
6. Process for the preparation of pure tita 70
nium. dioxide having rutile crystalline structure
which comprises adding an aqueous solution of
70 is compatible with the strongly acid solution used.
Solutions of these acids, most conveniently the
_
titanium tetrachloride to hot water containing
‘a small amount of. the sulfate ion, heating
It will be understood that the aforegoing the mixed solutions to hydrolytically precipi- '
8,118,946
3.
tate non-peptized hydrous titanium oxide in
readily ?lterabie form, separating the so ob
tained hydrous titanium oxide and calcining it
includas hydrolytic precipitation 01' hydrous tita
at a temperature between 700° C.'and 1000“ ‘C.
‘ing an aqueous titanium tetrachloride solution
containing a ‘small amount of a coagulant se 6
to ,rutile crystalline structure.
7. Process for the‘ preparation oi’ pure tita—
nium dioxide havingrutile crystalline structure
which comprises adding an aqueous solution of
nium oxide irom an aqueous titanium tetrachlo
ride solution, the step which consists in heat
lected from the group consisting of the acids
and alkali metal salts oi’ the sulfate. tartrate
and oxalate radicals to hydrolytically precipitate
titanium tetrachloride to hot watercontaining a
non-peptized, readily ?lterable hydrous titani
small amount of the tartrate ion, heating the
mixed solutions to hydrolytically precipitate non
um oxide.
10
11. In a processvi'or the preparation of pure
peptized hydrous titanium oxide in readily ?l
titanium dioxide having rutile structurev which
terable form, separating the so obtained hy
includes hydrolytic precipitation of hydrous tita
drous titanium oxide and calcining it at a tem
nium oxide from an aqueous titanium tetrachlo
perature between 700° C. and 1000° Q. to rutile ~rlde solution, the. step which consists in heat 15'
crystalline structure.
ing an aqueous titanium tetrachloride solution
8. Process for the preparation of pure tita
containing a small amount oi the sulfate ion to
nium dioxide having rutile crystalline structure
hydrolytically precipitate non-peptized, readily
which comprises adding an aqueous solution of
titanium tetrachloride to hot water containing‘
a small amount of the oxalate ion, heating the‘
mixed solutions to hydrolytically precipitate non
peptized- hydrous titanium oxide in readily ?i
terable form, separating the so obtained hydrous
illterable hydrous titanium oxide. 0
12. In a process for the preparation of pure
titanium dioxide having rutile structure which’
includes hydrolytic precipitation of hydrous tita- ,
nium oxide from an aqueous titanium tetrachlo
ride solution, the step which consists in heat
titanium oxide and calcining it at a tempera- _‘ ing an aqueous titanium tetrachloride solution
ture between 700° C. and 1000" C. to rutile crys
containing a small amount 0! the tartrate ion to
talline structure.
.hydrolytically precipitate non-peptized, readily
9. In a process for the preparation oi’ pure ?lterable hydrous titanium oxide.
titanium dioxide having rutile structure which
13. In a process for the preparation oiv pure
‘ includes hydrolytic precipitation of hydrous tita
nium oxide from an aqueous titanium tetrachlo
titanium dioxide having rutile structure which,
includes hydrolytic precipitation 01' hydrous tita
ride solution, the step which consists in heating
nium oxide from an aqueous titanium tetra
an aqueous titanium tetrachloride solution con
taining a. small amount of a
nega
heating an aqueous titanium-tetrachloride solu
tive,.divalent ion to hydrolytically precipitate
non-peptized. readily ?lterable hydrous titanium
ion to hydrolytically precipitate non-peptised,
oxide.
10. In a process for the preparation of pure
titanium dioxide having rutile structure which
chloride solution, the step which consists in
tion containinga small amount of the oxalate
readily ?lterable hydrous titanium oxide.
' .
vWilli-‘1211112 W. PLECHNEB.
ARTHUR W. B12808.